Fluidic fuel metering system



United States Patent [50] Field of Search.....

Inventors Appl. No.

Filed Patented Assign FLUIDIC FUEL METERING SYSTEM 9 Claims, 6 Drawing Figs.

U.S. Cl.

261/69,26l/40,26l/65.26l/73,26l/l21;137/815.

Int. Cl. F02m 7/04 26l/l21.l,

I9, 20. 34. 35, 36.], 65, 69(F.A. Digest), 70, 73,

[ 5 6 References Cited UNITED STATES PATENTS 3,061,286 10/1962 Mennesson 261/36(.l)UX 3,302,935 2/1967 York,.1r. 261/36(.l)X 3,386,710 6/1968 York,.lr. 26l/36(.l)UX 3,389,894 6/1968 Binder 261/36 Primary Examiner-Tim R. Miles Att0rney-Noel G. Artman ABSTRACT: A carburetor construction for metering liquid fuel for delivery downstream of the throttle valve to a sparkignition engine comprising only one fuel delivery system for all engine operating conditions including idling as well as full load conditions. The system, except for float bowl fuel inlet control and variable throttle valve, employs a fluidic device but no moving parts. Recycling of fuel in excess of engine demand to the fuel supply reservoir is avoided as well as any necessity for a secondary source of fluid pressure or a secondary fuel 40; 137/815 system for engine idling.

l l r l 'f IO 22 1 1 i i 3/ X\ 32 4 I k 7 4 2 /6 Y36 26 X 17,20 4. i 5351? Z I'\ I i\ l i i Ii i Patentcl Dec. 1, 1970 Sheet 1 of 2 INVENTORS EDWARD F. FORT WAYNE E. BERNDT F LUIDIC FUEL METERING SYSTEM BACKGROUND OF THEINVENTION This invention relates to a liquid fuel ma metering system for a spark-ignition internal combustion engine. More in particular this invention relates to a carburetor construction employing a fluidic device for metering liquid fuel for delivering all or substantially all fuel through nozzle means positioned downstream of the throttle control valve in a manner wherein the system singularly is capable of supplying fuel to the engine at a substantially constant air-fuel ratio for all loads imposed upon the engine and yet permit the engine to idle under the same system. In short a single fuel system is provided for all engine operating conditions including both idling and full load conditions.

A striking advantage in the engine fuel supply system of this invention is its ability to meter and deliver fuel into a zone of relatively high vacuum and turbulence (i.e. downstream of the throttle). Delivery into such a zone is advantageous in that it breaks up the liquid fuel and mixes it more evenly with the airstream thus promoting good cylinder-to-cylinder fuel distribution. Good cylinder-to-cylinder fuel distribution is important in allowing an engine to run steadily and smoothly with lean fuel-air ratio mixtures.

It will be noted that in the present invention the control of fuel flow to the engine is basically accomplished by controlling the rate of fuel supplied to a single outlet from a source having no external applied auxiliary pressure.

The prior art carburetor constructions usually provide two fuel metering systems of which the first is employed to deliver fuel upstream of the throttle valve during operating conditions imposing a load upon the engine and the second system delivers fuel downstream of the throttle valve for engine idling operating condition. Thus transition from one system to the other system during operation is is required whereas in the present invention such transition is avoided. U.S. Pat. No. 3,386,710 illustrates a fluid metering system employing a fluid amplifier wherein the flow of liquid fuel is split into two streams, one of which discharges through a nozzle into the airflow conduit to the engine above the throttle valve and the other stream discharges its liquid fuel presumably to a fuel reservoir for recycling while fluid amplifier pressure signal means are employed to proportion the flow between the two streams.

SUMMARY OF THE INVENTION The principal object of this invention is to provide a fluidic fuel metering system for a spark-ignition internal combustion engine which system singularly is capable of delivering all or substantially all metered fuel through a single liquid fuel outlet directed to a nozzle positioned downstream of the throttle control valve.

Another important object of the invention is to provide a fluidic fuel metering system according to the preceding object wherein no portion of liquid fuel is directed back to the fuel reservoir for recycling.

A further important object of the invention is to provide a fluidic fuel metering system according to the preceding objects wherein no external-or auxiliary secondary source of pressure is required.

Yet another important object of the invention is to provide a fluidic fuel metering system according to the preceding objects wherein the fuel metering requirements are met according to engine demand and accomplished without requiring moving parts for metering.

Still another important object of the invention is to provide a fluidic fuel metering system according to the'preceding objects which is capable of operating an internal combustion engine employing substantially constant lean fuelair ratios throughout all or nearly all of the range of engine load.

These and other desirable objects inherent in and encompassed by the invention will become more apparent from the ensuing description of preferred embodiments, the appended claims and the annexed drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of a carburetor construction having a fluidic fuel metering system of the present invention;

FIG. 2 is a view in vertical section taken along the line 2-2 of FIG. 1 showing details of the fluidic fuel metering system of the present invention;

FIG. 3 is a fragmentary view partly in section taken on line 3-3 of FIG. 2, illustrating certain ports'opening into the airflow conduit of the carburetor construction of the present invention;

FIG. 4 is a view in horizontal section taken along the line 4-4 of FIG. 2 illustrating the fluidic device of the fuel metering system of the present invention more in detail;

FIG. 5 is similar to FIG. 1 but represents a modified form of the present invention wherein the shape of the fluidic device is modified and positioned in the central portion of the airflow conduit; and

FIG. 6 is a view in vertical section taken along the line 6-6 of FIG. 5 illustrating the modified form of the fluidic device in detail.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 4 of the drawing the fluidic fuel metering system or carburetor of this invention is indicated generally by the numeral 10. The carburetor 10 includes an inlet airflow conduit 11 having its upper end in communication with the atmosphere, usually through a conventional air filter (not shown) and its lower end in communication with the cylinders through an intake manifold, of an internal combustion engine (not shown). Air flowing through the conduit 11 is controlled by a conventional throttle valve generally in dicated at 12 which is varied by a rotational movement of the throttle valve shaft 13 in a conventional manner.

The conduit 11 includes a restriction or venturi portion 14 which reduces the static pressure of air flowing therethrough to create control signal pressures related to the rate of airflow through the conduit 11 which will be discussed herein more in detail.

The carburetor 10 is provided with a conventional fuel float bowl or float chamber indicated generally at lSJThe chamber 15 includes a float 16 connected to an arm 17 pivotally connected at 18 to a side wall 19 of the carburetor 10. The arm 17 is provided with a valve element 20 in cooperative alinement with seat 21 in a conventional manner. A source of liquid fuel under pressure above atmospheric is connected to pipe 22 hereby liquid fuel is admitted into the float chamber 15 via conduit 22 and valve 20, 21 until the amount of fuel 23 in the float chamber 15 reaches a' predetermined fuel level 24 as indicated best in FIGS. 2 and 6. The upper portion of the float chamber 15 communicates with the upper portion of the inlet airflow conduit 11 through passage 31 having a port 32 opening into the conduit 11 as shown in FIGS. 1, 2 and 3.

The carburetor 10 is provided with a fluidic device generally indicated at 25 in FIGS. 2 and 4. The fluidic device 25 includes an interaction zone 26 having a restriction or inlet nozzle 27, shown best in FIG. 4, in communication with the float chamber 15 through fuel passage 28. Thus liquid fuel from the float chamber 15 may enter zone 26 through passage 28 and inlet port or nozzle 27.

The carburetor 10 is provided with a liquid fuel discharge member indicated generally at 29, closed at one end, extending into the inlet airflow conduit 11 and positioned below the throttle valve 12 as shown best in FIG. 2. The discharge member 29 includes one or more ports or orifices 30 also shown in FIG. 2. The discharge member 29 communicates with zone 26 of the fluidic device 25 through outlet port 33 and outlet passage 34 as indicated in FIGS. 2 and 4. Thus liquid fuel from the float chamber 15 is directed by the nozzle 27 through the zone 26 into port 33 from when whence it is conducted to the discharge orifices 30 through outlet passage 34 and discharge member 29.

The modified form of the carburetor 10' as shown in FIGS. 5 and 6 differs from the previously described carburetor 10 as shown in FIGS. 1 through 5 in 4 in that the fluidic device indicated at 25' is positioned centrally in the inlet airflow conduit 11 and, in addition is contained within a tubular element generally indicated at 35 as shown in FIG. 6. Liquid fuel from the float chamber 15 enters the zone 26' of the fluidic device through fuel passage 28 and nozzle 27'. From zone 26 the liquid fuel enters the dischargemember 29' through outlet port 33 and outlet passage 34. I

It will be noted from FIGS. 2 and 6 that the float chamber 15 is positioned with respect to the fluidic devices 25,25 whereby the fuel level 24 is maintained at or just slightly below the horizontal plane of the nozzles 27,27. If the fuel level 24 is above the nozzles 27,27 liquid fuel from the float chamber 15 will drain into the airflow conduit 11 during periods when the engine is notoperating which would result in loss of fuel and may affect the ability of the engine to start easily. On the other hand the fuel level 24 should not be substantially below the horizontal plane of nozzles 27,27 because it would then require an unnecessarily higher pressure difference to cause the liquid fuel to flow through the nozzles 27,27.

ln FlG. 4 it will be observed that the interaction zone 26 of the fluidic device 25 communicates with the airflow conduit 11 through the signal port opening 36. The distance between the nozzle 27 and the port opening 36 ideally should be zero. However, practically the distance between the nozzle 27 and pressure signal port opening 36 may be as much as about onehalf the total wetted perimeter of the port opening 36. A distance of 2 inches between the nozzle 27 and port opening 36 precludes satisfactory operation while a distance of about one-sixteenth inch provides very satisfactory operation. These same remarks apply equally well to the distance between the nozzle 27' and the port opening 36' shown in FIG. 6,

The aggregate cross-sectional areas of theorifices in the discharge member 29 is also important. It was found that the total or aggregate cross-sectional area of orifices 30 should preferably be from one-half to three times the cross-sectional area of the nozzle 27 or 27'.

Referring again to FIGS. 2 and 6 it will be noted that in the inlet airflow conduit 11 there are three principal signal pressure regions indicated at X, Y, and Z. The rate or metering of fuel 23 from the float chamber 15 through the'fluidic device 25,25 is a function directly related to the composite or integrated effect of the three absolute pressure magnitudes existing in regions X, Y, and Z during any predetermined operating condition of the engine. The absolute pressure at region X has been found to be slightly below atmospheric pressure and varies only slightly under all engine operating conditions. The absolute pressure in region Y at the venturi portion 14 of the airflow conduit 11 reaches its lowest value when the throttle 12 is at maximum open position (i.e. maximum throttle engine operation) and rises progressively to a maximum value somewhat below the absolute'pressure value in region X when the throttle 12 is nearly closed (i.e. operation of the engine at idling condition). The range of absolute pressure values in region Z has the widest variation. During operation of the engine at idling condition the absolute pressure value in region Z is very low, that is to say a pressure value of much. lower magnitude than that found in regions X or Y under any engine operating condition. On the other hand when the throttle 12 is at wide open position (i.e. engine operating at full load) the absolute pressure value in region Z will be slightly greater than the corresponding pressure value in region Y.

In operation, from the above, it will be apparent that under all engine operating conditions the absolutepressure value in region X will always be greater that than at either region Y or region Z. Therefore the air pressure in the float chamber 15 will drive the liquid fuel 23 through the nozzle 27,27. The nozzle 27,27 is so positioned that the liquid fuel emanating therefrom is directed toward the outlet port 33,33 and if the fluidic device 25,25 is properly arranged all fuel delivered into the conduit 11 will preferably be through the orifices 30 during any engine operating condition. Otherwise at wide open throttle or near wide open throttle engine operating condition some fluid may enter the airflow conduit through the port opening 36,36. Fluidic devices 25,25 constructed substantially as shown in FIGS. 4 and 6 in relation to the entire structure 10,10 have been found to deliver substantially all fuel through orifices 30, virtually none emanating from port opening 36,36 even at wide open throttle engine operation. Furthermore, the carburetors, as shown in the drawing, are capable of delivering to the engine fuel at a substantially constant airfuel ratio at any time the engine is under load (i.e. not idling condition).

Having thus described preferred embodiments of the invention, it can now be seen that the objects of the invention have been fully achieved and it must be understood that changes and modifications may be made which do not depart from the spirit of the invention as disclosed nor from the scope thereof as defined in the appended claims.

.We claim:

1. An internal combustion engine fuel metering system comprising:

a. an inlet airflow conduit having a venturi portion disposed therein capable of generating a first signal pressure region in said venturi portion and a second signal pressure region upstream of said venturi portion in an airstream flowing therethrough;

b. said conduit having a throttle valve means positioned downstream of said venturi portion capable of generating a third signal pressure region in said airstream downstream of said throttle valve means;

c. a liquid fuel discharge member positioned in said third signal pressure region for discharging liquid fuel into said airstream;

d. a fluidic device having an interaction zone positioned in adjunctive relation to said venturi portion of said conduit;

e. said fluidic device having a pressure signal port opening connecting said first signal pressure region with said interaction zone;

f. fuel outlet means communicatively connecting said interaction zone of said fluidic device with said discharge member;

g. a source of liquid fuel under pressure proportional to the pressure in said second signal pressure region; and

h. fuel inlet means communicatively connecting said interaction zone of said fluidic device with said source of liquid fuel whereby the integrated pressure values of said signal pressure regions regulate the rate of flow of fuel through said fuel inlet means to said interaction zone and said fuel discharge member thereby converting said airstream to an air-fuel mixture stream of substantially constant air-to-fuel ratio.

2. An internal combustion engine fuel metering system according to claim 1 wherein said fuel inlet means is positioned to discharge liquid fuel into said interaction zone toward said fuel outlet means.

3. An internal combustion engine fuel metering system according to claim 2 wherein said fuel outlet means includes an outlet port adjacent said interaction zone for receiving fuel from said zone and said fuel inlet means includes a nozzle positioned adjacent said zone in spaced relation from said outlet port.

4. An internal combustion engine fuel metering system according to claim 1 wherein said fuel inlet means includes a nozzle positioned adjacent said interaction zone and at a distance from said first signal pressure region not exceeding one-half the length of the perimeter of said pressure signal port opening.

5. An internal combustion engine fuel metering system according to claim 1 wherein said fuel inlet means includes a nozzle positioned adjacent said interaction zone and said fuel discharge member includes at least one orifice positioned to discharge fuel into said airstream.

6. An internal combustion engine fuel metering system according to claim 5 wherein the aggregate cross-sectional area of said orifices is within the range of one-half to and including three times the cross-sectional area of said nozzle.

tion of said chamber communicatively connected to said second signal pressure region.

9. An internal combustion engine fuel metering system according to claim 8 wherein means are provided in said chamber for limiting the entry of liquid fuel therein to a predetermined fuel level, said fuel level being slightly below said interaction zone of said fluidic device. 

